1. Field of the Invention
This invention pertains generally to mechanically-driven musical instruments which reproduce pre-recorded music, and specifically to operation of solenoid actuators using digitally mapped pulse signals to re-create the expression effects in the original music.
2. Description of the Background Art
Methods and apparatus for recording and playing back music on mechanically-driven instruments such as pianos are well known. For example, U.S. Pat. No. 4,744,281 issued to Isozaki on May 17, 1988, discloses an automatic player piano system with an ensemble playback mode for decoding a piece of music having at least two data blocks, one data block corresponding to music to be reproduced by an electronic sound generator and the other corresponding to music to be reproduced by activating solenoids to strike piano strings. U.S. Pat. No. 4,419,920 issued to Ohe on Dec. 13, 1983, discloses an apparatus for recording and reproducing musical performances in which the recording comprises the image, the sound, and musical instrument performance data of a particular performance, the watcher-listener being able to see and hear the performance via a video playback and the automatic playing of an actual musical instrument. U.S. Pat. No. 4,351,221 issued to Starnes et al. on Sept. 28, 1982, discloses a player piano recording system which has photosensor flags secured to the underside of the piano keys, vertical movement of which is detected by horizontally adjustable photosensors to produce "key played" and key velocity signals which are supplied to a microprocessor for deriving expression signals for recording on magnetic tape. U.S. Pat. No. 3,905,267 issued to Vincent on Sept. 16, 1975, discloses an electronic player piano with record and playback features. U.S. Pat. No. 3,604,299 issued to Englund on Sept. 14, 1971, discloses a method and apparatus for recreating a musical performance using pulse streams applied to relays or other drivers.
It is important, however, not only to record the musical notes and timing for later playback on an instrument, but also to record the expression contained in the original work in order to re-recreate a more realistic performance. Examples of methods and apparatus for recording expression effects can be seen in U.S. Pat. No. 4,172,403 issued to Campbell et al. on Oct. 30, 1979, which discloses a method and apparatus for encoding expression data while recording from the keyboard of an electronic player piano wherein the intensity of the music being recorded is reflected in variations in the power of the acoustic waveform produced; U.S. Pat. No. 4,176,578 issued to Campbell et al on Dec. 4, 1979, which discloses a system for encoding of bass and treble expression effects in a digital data stream while recording from the keyboard of an electronic player piano; and U.S. Pat. No. 4,174,652 issued to Campbell on Nov. 20, 1979, which discloses a method and apparatus for recording digital signals for later actuating solenoids for re-creation of musical expression.
Essential to accurate reproduction of the original work is the capability to decode recorded expression information and direct that information to the instrument being used to re-create the original work. In a typical application such as a player piano system, solenoids or other drivers are actuated to strike the strings. Several techniques and devices have been developed in an attempt to achieve "true reproduction" as can be seen in U.S. Pat. No. 4,132,141 issued to Campbell et al. on Jan. 2, 1979, which discloses a solenoid-hammer control system for re-creating expression effects from recorded music in which a stream of pulses activates the solenoids, the width of the pulses being modulated so that the average drive energy applied to the solenoid is proportional to the desired intensity; and U.S. Pat. No. 4,135,428 issued to Campbell on Jan. 23, 1979 which discloses a pulse width modulation circuit for controlling the expression of an electronically controlled keyboard instrument by simultaneous adjustment of both the leading and trailing edges of pulses in a pulse stream without varying the rate of the pulses, the pulses switching a solenoid on and off at a rapid rate so that the energy applied to the solenoid varies and therefore the striking force of the piano is changed. These approaches, however, use pulse streams to actuate solenoids or other drivers which do not contain sufficient expression information to achieve "true reproduction" of the original work, even though they modulate the width of pulses to vary the average drive energy and striking force. Furthermore, they are not capable of compensating for non-linear travel of the solenoid plungers or the mass of the strike keys differing from instrument to instrument.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant's acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicant's claimed invention.